Analysis of the skeletal remains of this four-year-old boy has revealed that he may be a Neandertal-Cro-Magnon hybrid. (Courtesy João Zilhão) [LARGER IMAGE]

Analysis of the skeletal remains of a four-year-old child buried in a Portuguese rock-shelter 25,000 to 24,500 years ago has yielded startling evidence that early modern humans and Neandertals may have interbred. While the boy's prominent chin, tooth size, and pelvic measurements marked him as a Cro-Magnon, or fully modern human, his stocky body and short legs indicate Neandertal heritage, says Erik Trinkaus, a paleoanthropologist at Washington University in St. Louis. Interbreeding could answer the vexed question of the fate of the Neandertals, the last of whom disappeared from the Iberian Peninsula 28,000 years ago.

Trinkaus was summoned to Portugal after archaeologists searching for rock art in the Lapedo Valley, 85 miles north of Lisbon, found the burial this past December. João Zilhão of the University of Lisbon, the excavation's director, described the skeleton's preservation as "miraculous"--only the skull and right arm were badly broken. The boy is the first Palaeolithic burial ever excavated on the Iberian Peninsula, and among the oldest modern humans ever scientifically excavated.

Trinkaus, who compared the boy's limb proportions with those of Neandertal skeletons, including some children, says that the body is the first definite evidence of a mixture between Neandertal and early humans. While full Neandertals are thought to have been extinct for 4,000 years before the boy was born, he appears to be a descendant of generations of Neandertal-Cro-Magnon hybrids. Neandertals belong to our species and contributed their genes to European ancestry, he says.